1. Field of the Invention
The present invention relates to a manufacturing apparatus equipped with a deposition apparatus in an evaporation step of carrying out deposition by vaporizing a material (hereinafter, referred to as an evaporation material).
2. Description of the Related Art
In recent years, research on a light-emitting device having an electroluminescence element (hereinafter, referred to as an EL element) as a self-luminous type light-emitting element is advanced. Especially, an EL element having an organic compound is also referred to as organic EL or an organic light emitting diode (OLED). The light-emitting devices using these elements have properties such as high response speed appropriate for an animation display, driving with low voltage or low power consumption; therefore, the devices are widely drawn attention as a next-generation display, especially as a flat panel display as well as a new-generation cellular phone or a personal digital assistant (PDA).
The structure of an El element is a laminated structure in which a layer containing an organic compound (hereinafter, referred to as an EL layer) is sandwiched between an anode and a cathode. An exciton is generated by recombining an electron hole and an electron in the EL layer by applying an electric field to an anode and a cathode. When the electron of exciton returns to a ground state, an energy difference between an excited state and the ground state is extracted as light. There are fluorescence that is emitted when the electron return from a singlet excited state to a ground state and phosphorescence that is emitted when the electron return from a triplet excited state to a ground state as light emission from the EL element.
The above EL layer has a laminated layer structure typified by “a hole transporting layer/a light-emitting layer/an electron transporting layer”. An EL material that forms an EL layer is roughly divided into a low molecular weight based (monomer-based) material and a high molecular weight based (polymer-based) material. A low molecular weight based material is generally formed by using an evaporation apparatus.
In a conventional evaporation apparatus, a substrate is placed in a substrate holder and an evaporation container that is filled with an evaporation material having an EL layer, a shatter that prevents an evaporation material to be evaporated from ascending, and a heater that heats the EL materials in the chamber are included. In the above evaporation apparatus, the container is heated by heating the heater; therefore, heat is transmitted to the material. Then, the evaporation material that reached at an evaporation temperature is evaporated and formed over a rotating substrate. However, since the evaporated evaporation material has a width in proportion to a distance to the substrate, a distance between the substrate and the container in which the evaporation material is filled needs to be spaced for 1 m or more to carry out uniform deposition over a large-sized substrate.
In such conventional evaporation apparatus as mentioned above, the apparatus itself is enlarged and it takes longer time for evacuation of each film formation chamber of the evaporation apparatus as a size of a substrate area is bigger. Therefore, when a chamber is exposed to an atmosphere to exchange a material, a evaporation to form a film cannot be carried out for a long time and decreases a throughput, which are problems. Also, in carrying out deposition over a large-seized substrate, a film thickness is uneven at a central part and a periphery part, and further, it is necessary to rotate a substrate that is facing down. Therefore, there is a limitation to apply an evaporation apparatus to a large-sized substrate.
In addition, when an EL layer is formed by evaporation, most of the evaporated evaporation material is adhered to the inner wall of the film formation chamber, the shatter, or a contamination shield (a protective plate preventing a evaporation material from being adhered to the inner wall of the film formation chamber) of the evaporation apparatus. Therefore, during film formation of an EL layer, utilizing efficiency of the expensive evaporation material is quite low for about 1% or less and the manufacturing cost of the light-emitting device is extremely high.
As one means for solving such problems as mentioned above, the evaporation apparatus (Reference 1: Japanese Patent Laid-Open No. 2001-247959 and Reference 2: Japanese Patent Laid-Open No. 2002-60926) is proposed by this applicant. This evaporation apparatus is an apparatus in which deposition is carried out by fixing a substrate and by reciprocating an evaporation source, which is superior in film uniformity of a large-sized substrate compared to evaporation according to the conventional substrate rotating system. Furthermore, material efficiency gets well since a distance between the substrate and the evaporation source is close, and there is an advantage in reduction of the manufacturing cost.
Many evaporation materials are needed in a large-sized substrate, and a small evaporation container is soon emptied of the evaporation material. Therefore, the number of evaporation container is increased and they are exchanged frequently. However, deposition time per substrate gets longer for a large-sized substrate; therefore, there is high possibility that an evaporation material is run out during film formation. Furthermore, throughput is decreased due to surplus heating time. Thus, it is necessary to enlarge an evaporation container to be filled with a large amount of evaporation materials to evaporate for a long time.
As for a kind of an evaporation container, a boat type shown in FIG. 6A and a crucible type shown in FIG. 6B or 6C are general, and a crucible type that is capable of being filled with a large amount of evaporation materials is appropriate for using as a mass-production apparatus.
Although such evaporation containers can be filled with quite large amount of evaporation materials, the thermal capacitance of the evaporation container and the evaporation material are large; therefore, temperature of the entire evaporation container tends to be uneven. Compared to the bottom part of the evaporation container, temperature at the upper part thereof including an opening likely to be low since it is difficult to heat directly with a heater and a large amount of heat is escaped. Therefore, a particle evaporated from an evaporation material (hereinafter, referred to as an evaporation particle) is cooled at the opening, and then adhered to the opening. Then, once the evaporation particle is adhered, the particle continues to grow as a core, and lastly the opening of the evaporation container is clogged with the evaporation material and the evaporation material does not scatter; therefore, further film deposition is impossible, which is a problem.
On the other hand, in order to exchange the evaporation container set at an evaporation source, the upper part of the evaporation source needs to be opened since it is easy to be removed. In addition, a space for removing the evaporation container is necessary between the evaporation source and the evaporation container, and since a heat portion and the chamber do not contact with each other, a heating system with radiant heat is adopted as a heating method.
However, there is a problem that the radiant heat escapes easily and the upper part of the evaporation container is unlikely to be heated since the upper part of the evaporation source is opened. Therefore, there is a difference between temperature at the bottom part and the upper part of evaporation container, and the evaporated evaporation material is cooled at the upper part of the evaporation container, which generates a problem that the material clog at the opening. Specifically, an evaporation material with high evaporation temperature is likely to generate temperature difference and evaporation is difficult.